This invention relates to magnetoresistive heads used in magnetic recording units.
Magnetic heads using a magnetoresistive effect of ferromagnetic materials are required to use the linear part of a change of the magnetoresistive effect upon the magnetic fields. For this purpose, usually a shunt film, a soft magnetic film, and a permanent magnet film are placed adjacent to the magnetoresistive film as a means to apply a bias magnetic field. This invention relates to a soft magnetic film of a magnetoresistive element using a soft magnetic film, more particularly of a magnetoresistive element having a cross sectional structure comprising a crystallized soft magnetic film/a spacer metal film or a spacer insulator film/a magnetoresistive film. Coventional technologies pertaining to such a crystallized soft magnetic film are described in U.S. Pat. No. 4,663,685 and No. 5,001,586, Journal of Applied Physics, Vol. 69, No. 8, 1991, pp. 5631-5633, etc.
The soft magnetic films used as means to apply a bias magnetic field in a magnetoresistive element has various significant problems to be solved such as corrosion resistance, cost, dispersion of magnetic characteristics and aging reliability in addition to the magnetic characteristics. Although the conventional films made of NiFe--Rh alloy have excellent corrosion resistance and other characteristics, 20 to 25 at. % of expensive rhodium Rh must be added to NiFe, which increases its material cost. Contrarily, alloy films obtained by adding niobium Nb or zirconium Zr to NiFe are lower in cost than the NiFe--Rh alloy films, but their demerits are poor corrosion resistance, wide dispersion of magnetic characteristics, and great aging change. As for amorphous magnetic films, the initial layer deposited on the substrate is easily crystallized and the dispersion of magnetic characteristics and the change by heat treatment are very great.